Method for preparing hides using mold tryptases, and a neutral to weakly acid reaction



Patented Sept. '17, 1940 UNITED. STATES PATENT-l OFFICE METHOD FOR reime HIDES USING I I MOLD 'TRYPTASES,

WEAKLY ACID REACTION AND A NEUTRAL T 0.

Otto Riihm, Darmstadt, Germany 8 Claims.

10 jecting alkali-swelled skins-or hides to a treat- -ment with moldtryptases and a water-soluble bisulphi-te, that is, a substance capableof supplying HSO3-ions, and, if desired, an ammonium salt, the methodbeing carried out in a neutral to weakly acid solution.

Ithas now been found that in the production of hides, fresh, salted, ordried skins or hides can be treated advantageously without alkalipretreatment with mold tryptases and substances 20, which yieldHSOs-iOIlS, e. g. a water-soluble bisulphite or sulphurous acid, with orwithout the addition of small .amounts of alkaline reacting substances,the process being carried out in a neutral to weakly acid solution. Thecustomary preliminary water soaking is eliminated by the new method, orelse appreciably shortened.

The method may be practiced by using the mold tryptases in conjunctionwith ammonium salts. Dried hides can be advantageously treated directwith the mold tryptase and the addition agents mentioned, without anypreliminary water soaking. -In the case of salted hides, a shortpreliminary treatment with water may be used. But even thewashing out ofthe common salt (NaCl) may be dispensed with.

It is surprising that it is possible in such a simple manner to converteven skins or hides which have not been preliminarly alkali treated intoa condition ready for dehairing, by treatment 40 with mold tryptase andasubstance capable of supplying HSOz-ions.

In accordance with the invention, the treatment of the skins and hideswith mold tryptase and a substance capable of supplying HSOa-ions, to-

5 gether, if desired, with further addition agents, can be carried outin any suitable manner, e.--g. in a pit, in a fulling barrel, or bycoating the hides with the treating material. The operation may becarried out at Ordinary temperature orat a somewhat raised temperature.For example, hides coated with the treating material may be hung up at25-30 C.

The tryptases used in accordance with the invention may be obtained fromsuitable molds, especially from the aspergillus' varieties, e. g.

Aspergillus flaws, Asperyillus parasiticus, Asper gillus efiusus,Aspergillus oryzae, and Aspergillus wentii.

The method in numerous respects possesses ad-' vantages over the methodset forth in my applica- 5 tion Serial No. 70,890, now patent'as notedsupra. The elimination of the alkaline pre-swelling makes it possible tospare the skin and also serves to save one Working step.. The softeningand hair-loosening operations may be combined into a single workingstep. '80 to speak the dehairi ng may be eifected by the softening step,while yet sparing the skin. 'This is not possible to the sameadvantageous degree either-with mold tryptase alone or with substanceswhich supply HSOa-ions when taken alone. '7

It is however also possible, within the scope of the invention, tosupplement the treatment '(i. e. e 7 involving the use of mold tryptaseand a substance capable of supplying HSO3-ions and with the procedurecarried out in neutral to weakly acid solution) with an alkalineafter-treatment prior to dehairing. For example, the treatment maybeinterrupted before the loosening of the hair is fully accomplished, andthe process carried on in weakly alkaline reaction with the moldtryptase and using as an activator the sulphite formed from thebisulphite or sulphurous acid when the material is rendered alkaline.

The dehairing may-be followed by an alkaline after-treatment withalkaline reacting salts or alkalies or alkaline earths, with or withoutthe addition of other dehairing agents. The more or less thoroughremoval of these alkaline reacting compounds may be eifected by awashing-out procedure or by the action of neutralizing or delimingagents. If desired, this procedure may be combined with a treatment withenzymes having a bating action.

Example 1 I 100 kg. salted cattle skins are fulled for one hour with:'

Water of ordinary temperature liters 300 Thereupon, v

Sodium bisulphite kilo grams 2 Mold tryptase do 2 dissolved in 20 litersof water are added. The

fulling is again repeated for one hour, where upon the skins are allowedto rest until they are in a dehairable condition which, in general,takes about five days, The action is'carried out at a and'after-treatedfor one day with Per cent Water 300 Calcined soda (figured on the peltweight) 6 After removal from the soda solution, the hides are hung incold water over night then sheared, smoothed, and pickled or tannedwithout any subsequent bating.

Example 2 100 kg. salted cattle skins are washed for /2 to 1 hour withrunning water and laid over night in fresh water.

After. this period, the skins are fulled in a barrel for an hour with asolution composed of 4 .Sodium bisulphite kilograms 2 Mold tryptase do 2Water liters 300 and then allowed to rest soplong until they are in adehairable condition. This occurs after about four days. The actiontakes place at a pH value of 5.5 to 6. The further treatment'of theskins is effected as in Example 1.

Example 3 100 kg. of dried lamb skins are softened for 1 to 2 days with:

Water of ordinary temperature liters 1000 Sodium bisulphite w..-k'ilograms 4 Mold tryptasedo. 4

Per cent Water 300 Calcined soda (figured on the pelt weight) 6 for from1 to 5 days, depending on the kind of leather desired. After removal offlesh, smoothing and washing, the hides are pickled or tanned.

Example 4 Freshly removed sheep skins are sprayed with water on thefleshy side to remove blood and are then coated on the fleshy side witha solution consisting of:

Parts Water 10 Mold tryptase 2 Sodium bisulphite -a .2

pH value of 5.5 to 6. The skins are then dehaired and stored infolded-together condition for 24 hours. ,The action takes place at a pHvalue of 5.5 to 6. After this time, a solution of Parts Water 10Calcined so 2 is applied to the fleshy side. The hides are again foldedtogether and stored for l to 2 days. They are thn de-wooled andafter-treated with:

Per cent Water 300 calcined-soda (figured on the pelt weight) 6 Afteron'ormore days the flesh is removed and they are washed and pickled ortanned.

In lieu of 6% calcined soda, it is also possible to use 6% of 25%ammonia, or 6% calcium hydroxide for the after-treatment.

The duration of the after-treatment is governed by the kind of leatherdesired. When lime is used, a deliming treatment is employed at the endwith one of the known deliming agents, e. g. an ammonium salt. Ifdesired, the deliming may also be combined with a weak enzymatic hating.

I claim:

1. A method of producing ready-to-tan hides, which comprises, as aninitial step, treating fresh, salted, dried or partially water-soakedskins or hides with a mold tryptase in neutral to weakly acid solutionwith the addition of a substance which yields HSOa-ions, in the absenceof alkaline pre-treatment.

2. A method as set forth in claim 1, wherein the mold tryptase isobtained from an aspergillus variety.

3. A method as setforth in claim 1, wherein an ammonium salt is added tothe treating bath.

4. A method wherein dried hides or skins are treated as set forth inclaim 1 without any preliminary water-soaking.

5. A method wherein salted hides are treated as set forth in claim 1after a short preliminary water treatment.

6. A method as set forth in claim 1, wherein the skins or hides aretreated with an alkaline solution following treatment with moldtryptase.

'7'. A method as set forth in claim 1, wherein the skins or hides aretreated with an alkaline solution following partial treatment with themold tryptase but prior to dehairing.

8. A method as set forth in claim 1, wherein the skins or hides aretreated with an alkaline solution following treatment with the moldtryptase and after dehairing has taken place.

o'rro RGHM.

' CERTIFICATE OF CORRECTION. Patent No. '2,'215,o55. September 1 191m.

OTTO RESHM.

It is hereby certified that error appears in the above umberedpatentrequiring correction as follows: In the heading to the printed specifica tion line 7, for "Serial No. 2514,0148" read Serial No.2514.,OLL8. In Germany October 15, l937--; end that the said LettersPatent should be reed with this correction therein that the same mayconform to the record of the case mule Patent Office. 4

Signed and sealed this let day of April, A. D. 19in.

Henry Van Arsdale, (Seal) -Acting Commissioner of Patents.

